This invention relates to the cleaning of fabrics, and, more specifically, to an approach for removing non-particulate and particulate soil from fabric using a gas jet technique.
Garment dry cleaning is currently performed using organic solvents such as perchloroethylene or petroleum derivatives. These solvents pose a health hazard, are smog-producing, and/or are flammable. The use of dense-phase carbon dioxide (both liquid and supercritical) as a dry-cleaning solvent medium resolves the health and environmental concerns posed by conventional solvents. An additional benefit is that its use reduces secondary waste streams associated with processes that use conventional solvents. A dry-cleaning process that uses liquid carbon dioxide as a cleaning medium is described in U.S. Pat. No. 5,467,492. In one embodiment, the fabric is placed into a perforated basket within a pressure vessel, and then submerged into a pool of liquid carbon dioxide. The liquid carbon dioxide and the fabric in the pool are agitated by an incoming flow of liquid carbon dioxide that promotes a tumbling action of the fabric. The liquid carbon dioxide solvent promotes the removal of the soluble soils through their dissolution, and the mechanical action of the fabric tumbling promotes the expulsion of the soils that are particulate in nature (e.g., sand, dust, food particles, etc.).
One of the disadvantages of this liquid carbon dioxide process is that it must be performed within a pressure system, and thus has associated high capital costs. An apparatus and method are described in U.S. Pat. No. 5,651,276 to expel particulate soils from fabrics by gas jets at ambient pressure. This gas jet process may be practiced using the apparatus of the liquid carbon dioxide process described above, as a step of an overall fabric dry-cleaning process, or in a separate, low-cost apparatus. This approach has the disadvantage, when used by itself, that soluble and/or non-particulate type soils are not removed.
In the current commercial dry-cleaning process, localized soils and stains are chemically treated and the spots are removed on a spotting board, prior to processing the entire garment in the dry-cleaning machine. This localized soil removal from fabrics is termed xe2x80x9cspottingxe2x80x9d, and it involves the use of steam, and/or solvents to dissolve the soluble soils, and/or chemical agents to alter their composition. Once the soil alteration has occurred, the loosened soil is typically flushed and vacuumed out of the fabric. This procedure is performed manually and is labor intensive.
There is a need for an approach that realizes the advantages of the gas jet process, while permitting the removal of non-particulate soils in a commercially satisfactory and inexpensive manner. The present invention fulfills this need, and further provides related advantages.
The present invention provides a gas jet method for cleaning fabric that removes both non-particulate soil and particulate soil. Only a single processing apparatus is required, and both the non-particulate soil and the particulate soil are removed using that apparatus. The approach of the invention operates at atmospheric pressure within the gas jet processing container, and with moderate gas pressure. With this approach and its associated apparatus, gas jet cleaning of both particulate and non-particulate soil may be accomplished on either a commercial scale, as in a dry-cleaning establishment, or on a home scale. The approach is less labor intensive than conventional dry cleaning, and does not utilize the organic solvents used in dry cleaning and spotting.
The present invention provides an approach whereby soiled areas of fabric are first treated with a particulating chemical that loosens embedded non-particulate soil in a manner that renders it particulate in nature, and thus removable when exposed to a gas jet agitation process. In accordance with the invention, a method for cleaning fabrics comprises the steps of providing a piece of fabric, treating at least a portion of the piece of fabric with the particulating chemical, and agitating the entire piece of fabric with a gas jet to dislodge particulates therefrom. The gas jet dislodges and expels from the fabric both the soil that was initially particulate and the soil that has been rendered particulate by the particulating chemical. It is desirable to include an anti-static compound in the treatment to prevent redeposition of dislodged soil back onto the fabric and to prevent the fabric from tangling under the effects of the gas jet.
The particulating chemical may be of any operable type that dislodges an embedded non-particulate soil and converts the non-particulate soil into a particulate soil. The particulating chemical may be general in effect, and functional with a wide range of types of non-particulate soil, or may be selective to particulate a narrow range of types of non-particulate soils such as one or a few specific types of stains. After treatment with the particulating chemical, the article is then contacted with the particle dislodging gas to remove the particulated stain material as well as any previously present particulate soil. The particulating chemical is selected to be consistent with other features of the process, such as safety, biodegradability, and environmental acceptability.